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HARD  LEAD

247

trated ammonia and 1-2 c.c. of magnesia mixture. After about 24 hours,
the magnesium ammonium arsenate is collected on a filter, transformed
by ignition into pyroarsenate and weighed : Mg2As20- x 0-4827 = As.

(6) DETERMINATION OF THE ANTIMONY. The filtrate from the mag-
nesium ammonium arsenate is treated with ammonium sulphide and acidified
slightly with sulphuric acid. The antimony is thus precipitated as sulphide,
which is dissolved in ammonium sulphide, the solution being evaporated
in a tared porcelain crucible, oxidised with nitric acid, calcined gently and
weighed : Sbs04 X 0-7898 = Sb.

The refined lead of commerce, especially that destined for making electrical
accumulator plates, is a very pure metal, containing 99-96-99-99% Pb.

The compositions of samples of lead of different origins are as follows
(Schnabel, Hollard, Hampe) :

TABLE  XXIX
Composition of Samples of Lead

Origin.
	Pb
	Sb
	Ag
	c.
	Zn
	Fe
	Bi
	As
	Cd         Ni
	Mn

Pertusola •! * '
	99-9915 99-9937
	0-0050 0-0013
	o-ooi 0-0006
	0-0003
	0-0006 0-00085
	O'OOlfi
 0-0014
	O-OO2I
	-
	-         -
	-

Monteponi (Sardinia)
	99-99
	0-0030
	O-QOIO
	0-0005
	O-002I
	0-0047
	O-OOO7
	—
	—         —
	—

Pennsylvania  (Lead
	
	
	
	
	
	
	
	
	
	

Co.)     ....
	99-9924
	O-OOI2
	O-OOO2
	0-OOO2
	O-OOO/
	0-0017
	O-OO3O
	—
	—         —
	O-0002

Germany.
	99-9853
	0-0044
	O-OOO6
	O-OOO"
	O-OOO5
	O-OOI I
	0-OO73
	—
	trace     trace
	----


	
	
	
	
	Zn.Ni.Co
	
	
	
	
	

Spain (Penarroya)   .
	99-989
	O-OO3
	-----
	trace
	0-005
	0-012
	O-Ogi
	—
	i
	i

Sweden   ....
	99-9575
	O-OO4O
	trace
	0-0018
	0-0002
	0-0015
	0-0350
	trace
	trace  j    —
	~

HARD   LEAD

Hard lead or antimonial lead is an alloy of lead and antimony con-
taining small quantities of copper and tin and sometimes also iron, nickel,
cadmium, arsenic, etc., and serves for making type, the plates of certain
forms of electric accumulators and cast ornamental articles, and as anti-
friction metal, etc.

The essential determinations to be made on these alloys for a complete
analysis (see B] are those of the lead, antimony, copper and tin, determina-
tions of iron, nickel, arsenic, etc., not being always necessary. Often,
however, determinations of certain elements only are required (see Partial
Analysis).

A.   Partial Analysis

For special purposes, determinations of the copper and tin alone are
required.

1. Direct Determination of the Copper.—See Direct Determination
of Copper in White Metal.ion of the Arsenic and Antimony.—(a) DETERMI-